Drought Monitor: Locally heavy rain brings drought relief

Summary: Locally heavy rain provided drought relief in portions of the Southeast, while much-needed, locally heavy snow stabilized some western snowpacks. However, much of the west continued to wrestle with precipitation deficits and below-normal snow-water storage.

Mid-Atlantic and Northeast: The region’s first widespread winter storm dropped a mix of snow, ice, and rain. Liquid total precipitation equivalent was generally less than an inch, but was enough to stave off any expansion of Abnormal Dryness (D0) in New England and the lower Delmarva. Over the past 90 days, precipitation has tallied less than 70 percent of normal in southeastern Virginia and southern portions of the Maryland and Virginia Eastern Shore; rain or snow will be needed to prevent degradation into Moderate Drought (D1) over the upcoming weeks.

Southeast: Locally heavy rain in northern and western portions of the region contrasted with increasingly dry conditions farther south and east. A storm and its attendant cold front dropped 2 to 4 inches of rain across Alabama and northern and western portions of Georgia, resulting in some 1-category improvements in the latest drought designation. However, the rain largely bypassed the core Extreme (D3) to Exceptional (D4) Drought areas of Georgia, resulting in little if any improvements across central and southern portions of the state. In Florida, light to moderate showers (0.25 to 2.0 inches) were reported from the panhandle toward Ocala. Dry weather prevailed across the remainder of the state, which coupled with declining streamflows, elevated fire danger, and increasing short-term precipitation deficits resulted in expansion of Moderate Drought (D1) across Lake Okeechobee toward West Palm Beach. In northeastern Florida, Severe Drought (D2) was expanded southward toward Gainesville to reflect streamflows in the 5th percentile (or lower) and 90-day precipitation deficits of 6 inches or greater. Farther north, no change was made to the Carolinas , with many areas receiving a half inch or more of rain; however, the southern and eastern portions of North and South Carolina continue to teeter toward drought intensification, with short- and long-term Standardized Precipitation Indices (SPI) indicating varying degrees of Drought.

Delta: Scattered showers, some heavy, were reported across southern and eastern portions of the region. The heaviest rain, which tallied 2 to 3 inches in central Louisiana and southern Mississippi, brought some minor improvements to D0 (Abnormally Dry) and D1 (Moderate Drought) in these locales. The rest of the region remained unchanged.

South-Central U.S.: Despite dry, warmer-than-normal weather (temperatures averaging up to 14°F above normal), little if any change was made to the drought designation from Texas northward into southern Kansas. In fact, locally heavy rain has been falling over the region since the data cutoff time (12z Tuesday, January 24) for this week’s drought depiction; impacts from the rain will be addressed in next week’s U.S. Drought Monitor. A small increase in D0 (Abnormally Dry) was made in northeastern Oklahoma to reflect 60-day precipitation deficits up to 3 inches (locally more).

Central and Northern Plains: Seasonably cold conditions prevailed, with some snow falling from the northern High Plains eastward across northern South Dakota toward Sioux Falls. To the south of this area of snow, D0 (Abnormally Dry) conditions were expanded to include much of northern Nebraska. Precipitation in this area has totaled locally less than 50 percent of normal over the past 60 to 90 days, with the 3-month Standardized Precipitation Index (SPI) highlighting this same area as being unfavorably dry.

Midwest: Drought areas of the Midwest - which extend from northwestern Iowa into Minnesota and eastern-most portions of the Dakotas - reported mostly dry weather and seasonable temperatures (averaging within 2 to 4°F of normal) during the past week. Changes to drought designation were generally minor, and included expansion of Moderate Drought (D1) across northwestern Minnesota and northeastern North Dakota. Standardized Precipitation Indices (SPI) out to 6 months indicated increasingly dry conditions in this region. Likewise, 90-day precipitation totals are running 25 percent of normal or less north of Grand Forks, and soil moisture percentile rankings are in the 10th percentile or lower across much of northern Minnesota. On the other hand, drought impacts at this time of year are generally negligible and difficult to ascertain due to the cold; should drier-than-normal conditions continue, this area will have to be closely monitored as we ease into spring.

Western U.S.: Locally heavy, much-needed precipitation in western and northern portions of the region contrasted with ongoing dryness and increasing drought from the southern Great Basin into the central Rockies. A series of Pacific disturbances generated moderate to heavy rain and mountain snow from central California northward into the Pacific Northwest. Heavy snow was reported in the Sierra Nevada (3-8 inches liquid equivalent, locally more) and from the Klamath Mountains (10 inches or more liquid equivalent) into the Cascade Range. Snow-water equivalent in the Sierra improved, although many stations were still in the 20th percentile or lower. Nevertheless, the precipitation provided a 1-category improvement in drought designation in the Sierra, with D2 (Severe Drought) reduced to D1 (Moderate Drought). This area, however, will need to be closely monitored over the upcoming weeks, with water-year-to-date precipitation still averaging 50 percent of normal or less. The heavy precipitation in the Klamath Mountains likewise resulted in modest improvements to Abnormal Dryness (D0) and Moderate Drought, with water-year-to-date precipitation ranging from 50 percent of normal in the southern portions of the Klamath to near normal closer to the Oregon border. Heavy precipitation in the Cascades boosted snow-water equivalents into the 50th to 75th percentile (locally higher), with drought not a concern in the mountains of the Pacific Northwest at this time. Valley locales east of the Cascades largely missed out on the rain and snow, although a half inch or more in the D1 area from southern Washington into north-central Oregon provided beneficial moisture for winter wheat. In northern and central Idaho, moderate to heavy snow (2-6 inches liquid equivalent, locally more) boosted mountain snowpacks and alleviated Abnormal Dryness (D0). By week’s end, snow-water equivalents had jumped above the 40th percentile across much of the region, with yet another storm poised to provide additional relief to the southern portions of the state.

Meanwhile Moderate Drought (D1) was expanded from northwestern Nevada eastward across north-central Utah and into portions of northwestern and central Colorado, despite the arrival of some much-needed rain and snow. Even with the precipitation, which totaled a half inch or less at lower elevations to locally more than an inch (liquid equivalent) in the mountains, additional detailed assessment led to a general increase in drought designation. Water-year precipitation is running 50 percent of normal or less from northwestern and central Nevada eastward into Utah and Colorado. In particular, snow-water equivalent percentile rankings range from: 3rd to 15th percentile in east-central Nevada; 10th to 30th percentile in Utah’s central Wasatch and less than the 20th percentile in the Uinta Mountains; and 3rd to 30th percentile in northwestern and central Colorado. Further illustrating the dryness are the 3- and 6-month Standardized Precipitation Indices, which both depict D1 (or worse) conditions in the newly-expanded Moderate Drought (D1) region.

Across the southern Rockies and Southwest, no changes were made to the current drought classification. Precipitation in the shorter term (60 to 90 days) has been generally sufficient to prevent drought intensification, with current snow-water equivalent in the 40th percentile or higher over much of Arizona and New Mexico.

Alaska, Hawaii, and Puerto Rico: In Alaska, bitterly cold conditions continued, with temperatures averaging more than 20°F below normal. Snow continued to fall across the southern half of the state, with no concerns for drought. In Hawaii, much of the state was dry, although rain was reported on Kauai. With the ongoing dryness and reports of pastures in very poor condition, Extreme Drought (D3) was expanded northward on the Big Island, while Abnormal Dryness (D0) was expanded to encompass all areas from Oahu to the Big Island. On Puerto Rico, light to moderate showers (1-2 inches, locally more) fell across the northeastern quarter of the island, with no drought concerns at this time.

Looking Ahead: A moisture-laden storm system will provide widespread, locally heavy rain from central and eastern Texas into the Delta and Southeast, although rain is expected to diminish as a trailing cold front sweeps across Florida. Rain will also fall in the Mid-Atlantic and Northeast, with snow likely in northern New England. Meanwhile, the last in a rapid succession of Pacific storms will bring additional rain and mountain snow to the Northwest as well as the central and northern Rockies. Generally dry weather is expected to return to California and the Southwest. The NWS 6- to 10-day outlook for January 31 – February 4 calls for above-normal temperatures over much of the contiguous U.S., with cooler than normal conditions confined to southern Florida. Drier-than-normal weather is expected from the central and southern Rockies into California and from the southern Delta into the southern Atlantic Coast. Meanwhile, above-normal precipitation is anticipated from the central Corn Belt into the Great Lakes Region.

Author: Eric Luebehusen, U.S Department of Agriculture

Dryness CategoriesD0 ... Abnormally Dry ... used for areas showing dryness but not yet in drought, or for areas recovering from drought.